The Feasibility of Ultrasonography in Defining the Size of Jaw Osseous Lesions

Statement of the Problem Jaw bone lesions are common pathologic conditions. The role of ultrasonography in evaluation of the extra-osseous lesions is confirmed, however, this imaging modality is not the diagnostic routine for the intra-osseous jaw lesions. Purpose The purpose of this study was to evaluate the efficiency of ultrasonography in diagnosis of intra-osseous jaw lesions concerning their size and content and also to study its correlation with the histopathological findings. Materials and Method For this study, 15 patients with intra-osseous jaw lesions in the maxilla and mandible were selected from those referred to the Department of Oral Surgery. Panoramic imaging, computed tomography (CT) or cone beam computed tomography (CBCT) and ultrasonography (USG) were performed for all the lesions. The size of the lesions was measured by USG and then compared with CT or CBCT. Moreover, the correlation amongst the echographic patterns and histopathologic results was evaluated. Results In 12 cases, size values were in complete agreement with CT or CBCT. The size of 3 lesions could not be measured by the radiologist due to the thickness of buccal cortical plate. Conclusion Findings of this study suggested that USG might be feasible in estimating the size of intra-osseous jaw lesions with little underestimation. This study also confirmed that ultrasound imaging was a very useful imaging technique which could provide significant diagnostic information regarding the content of jaw bone lesions where the buccal bone thickness was thin enough.


Introduction
Imaging techniques play a crucial role in detecting, diagnosis, treatment and follow-up assessments of intra-osseous maxillofacial lesions. Because of the wide variation of jaw bone lesions, the diagnosis is often complex. [1][2] Following the advancements in technology, various imaging modalities have been introduced to pro-fessional use in this field; however, panoramic radiography is still the gold standard for the first-step twodimensional assessment of jaw lesions among other conventional techniques. [3] Despite its high radiation dose, Computed Tomography (CT) scan is being used regularly as an advanced complementary method in diagnosis of jaw bone lesions. [4] Cone beam computed tomography (CBCT) is a more recent alternative to panoramic radiography with the benefit of lower radiation exposure. [5] Meanwhile, ultrasonography (USG) has been frequently used in evaluating the solid and cystic nature of the lesions.
Although this technology is safe and non-invasive, its use in dental practice has been limited to soft tissues. [4] The number of studies investigating the role of ultrasound in evaluation of bony lesions is limited. In 1996, Lauria et al. [6] prospectively evaluated the role of ultrasonography as a complementary imaging modality in the diagnosis of intra-osseous jaw lesions.  [4] suggested that USG provided accurate information on the content of intra-osseous jaw lesions and Doppler ultrasound was capable of showing vascularization of such lesions.
The purpose of our study was to evaluate the intra-osseous jaw bone lesions by means of conventional radiography, CT or CBCT scans, and USG regarding the size and content of these lesions and to compare the correlation between the ultrasonographic findings and histopathologic results.

Materials and Method
Out of the patients referring to maxillofacial surgeons in Shiraz, 15 cases with intraosseous jaw lesions in the maxilla or mandible were enrolled in this study. After receiving approval from the Ethics Committee, all the patients consented to participate in the study and were informed about the techniques used and any potential risks or benefits. Size of all lesions was initially analyzed by using CT or CBCT. Measurements in CBCT scans were made using accurate inherent software by a maxillofacial radiologist with a precision of 0.1mm.
The size of the lesions in CT scans was measured by the scale supported for all slices. Any measurement was applied on the specific slice in which the lesion appeared with its largest dimensions.
An expert radiologist also measured the lesion size in the specific USG slice in which the lesion manifested its greatest dimension. The aforementioned data was then compared with CT or CBCT as gold standards.
Intraclass correlation coefficient (ICC) between both modalities (US and CT) was then evaluated to assess their agreement regarding size evaluation.
To facilitate the comparison with histopathologic results, USG findings were classified into the following 5 groups; anechoic: characteristic of cystic lesions because of liquid content; hypoechoic: characteristic of cystic lesions with dense liquid content (e.g., odontogenic keratocyst) and odontogenic tumors with semis-

Results
In this study, 15 intraosseous jaw lesions were assessed in 15 patients. Ten lesions were located in the mandible and 5 in the maxilla. The size measurement data of all lesions analyzed by CBCT/CT is displayed in  Table 3.

Discussion
As stated previously, only a limited number of studies have investigated the role of ultrasound in diagnosis of jaw bone lesions, particularly in evaluation of the size of these lesions.   ccal bone thickness is thin enough. Further studies in this field seem inevitable to clarify ultrasound findings.